[AD] What are the units of the radius in the color picker tool?

[Gear maker]

I don't believe I've ever seen this question or an answer for it before.  In the color picker tool there is a radius that can set to an area to be averaged for the color.  If I select a 5x5 area, how big is this area?  How do I know if a 5 unit square will cover the area I need and not bleed into an area not wanted?

All the Help says is: Radius—Choose to sample from directly under the cursor (Point 1x1) or from differently sized square areas where the color is averaged.

My guess is this is the number of screen pixels to be averaged.  So if I have about 109 pixels per inch on my screen, then each pixel is about 9/1000 of an inch.  So if I have selected 129x129 then everything that is in a square about 1-1/4 inch wide and high with the cursor centered in it will be averaged.  Regardless of the zoom.  So 5x5 would be an area about 0.046 inches (about 3/64") square.

So if I zoom in on a pixelated image where each displayed pixel is maybe 0.1" square a setting of 5x5 will still only read that pixel in the image.  When trying to average out a dithered image I would have to use a setting significantly larger setting or zoom way out.

Is this correct?

[Aammppaa]

The dimensions are pixels. 

Logically what you say sounds correct, but to be honest, I've never thought about it that way! 

I've always picked a size that grabs the sort of colours I want, purely by feel / intuition /experimentation. 

[Gear maker]

Aammppaa, I had always assumed it was pixels, but pixels in the drawing.  Because of that the amount of zoom didn't matter.  It was only lately that I started to figure out it was pixels on the display, so zoom was critical.  My main use was to average out a dithered image.  I doubt in the past I've had the area large enough most of the time to get a true representation of the actual color. 

I'm hoping one of the devs will confirm the math so I can note the sizes covered for each of the radius settings.  Also "radius" seems to be a misnomer as it would be a square area if I'm correct.